Introduce Checkout command handler

This commit includes the CheckoutBook command along with its corresponding command handler
and method.

src/lending/__init__.py

@@ -19,6 +19,7 @@
 
 from lending.app.dailysheet import DailySheet  # isort:skip
 from lending.app.patron.hold import PlaceHold  # isort:skip
+from lending.app.patron.checkout import CheckoutBook  # isort:skip
 
 
 __all__ = [
@@ -29,6 +30,7 @@
     "HoldStatus",
     "HoldPlaced",
     "Checkout",
+    "CheckoutBook",
     "CheckoutStatus",
     "Book",
     "BookStatus",

src/lending/app/patron/checkout.py

@@ -0,0 +1,23 @@
+from protean import current_domain, handle
+from protean.fields import Identifier
+
+from lending import Book, Patron, checkout
+from lending.domain import lending
+
+
+@lending.command(part_of="Patron")
+class CheckoutBook:
+    patron_id = Identifier(required=True, identifier=True)
+    book_id = Identifier(required=True)
+    branch_id = Identifier(required=True)
+
+
+@lending.command_handler(part_of="Patron")
+class CheckoutCommandHandler:
+    @handle(CheckoutBook)
+    def handle_checkout_book(self, command: CheckoutBook) -> None:
+        patron = current_domain.repository_for(Patron).get(command.patron_id)
+        book = current_domain.repository_for(Book).get(command.book_id)
+
+        checkout(patron, book, command.branch_id)()
+        current_domain.repository_for(Patron).add(patron)

src/lending/app/patron/hold.py

@@ -16,7 +16,7 @@ class PlaceHold:
 @lending.command_handler(part_of="Patron")
 class HoldCommandHandler:
     @handle(PlaceHold)
-    def handle_PlaceHold(self, command: PlaceHold) -> None:
+    def handle_place_hold(self, command: PlaceHold) -> None:
         patron = current_domain.repository_for(Patron).get(command.patron_id)
         book = current_domain.repository_for(Book).get(command.book_id)
 

tests/lending/app/bdd/checkout_handlers/features/check_out_a_book.feature

@@ -0,0 +1,10 @@
+Feature: Check Out a Book
+
+  Scenario: Patron checks out a book on hold
+    Given a circulating book is available
+    And a patron is logged in
+    And the patron has a hold on the book
+    When the patron checks out the book
+    Then the checkout is successfully completed
+    And the checkout has a validity of CHECKOUT_PERIOD
+    And the hold is marked as checked out

tests/lending/app/bdd/checkout_handlers/step_defs/checkout_steps.py

@@ -0,0 +1,75 @@
+from datetime import date, timedelta
+
+import pytest
+from protean import current_domain, g
+from pytest_bdd import given, then, when
+from pytest_bdd.parsers import cfparse
+
+from lending import CheckoutBook, HoldStatus, HoldType, Patron, PlaceHold
+
+
+@pytest.fixture(autouse=True)
+def reset_globals():
+    yield
+
+    if hasattr(g, "current_user"):
+        delattr(g, "current_user")
+    if hasattr(g, "current_book"):
+        delattr(g, "current_book")
+    if hasattr(g, "current_exception"):
+        delattr(g, "current_exception")
+
+
+@given("a circulating book is available")
+def circulating_book_available(book):
+    g.current_book = book
+
+
+@given("a patron is logged in")
+def patron_logged_in(regular_patron):
+    g.current_user = regular_patron
+
+
+@given("the patron has a hold on the book")
+def patron_has_hold_on_book():
+    command = PlaceHold(
+        patron_id=g.current_user.id,
+        book_id=g.current_book.id,
+        branch_id="1",
+        hold_type=HoldType.CLOSED_ENDED.value,
+    )
+    current_domain.process(command)
+
+
+@when("the patron checks out the book")
+def patron_checks_out_book():
+    command = CheckoutBook(
+        patron_id=g.current_user.id,
+        book_id=g.current_book.id,
+        branch_id="1",
+    )
+    current_domain.process(command)
+
+
+@then("the checkout is successfully completed")
+def checkout_completed():
+    message = current_domain.event_store.store.read_last_message(
+        f"library::patron-{g.current_user.id}"
+    )
+    assert message.metadata.type == "Library.BookCheckedOut.v1"
+
+
+@then(cfparse("the checkout has a validity of {validity_days_config}"))
+def checkout_validity(validity_days_config):
+    patron = current_domain.repository_for(Patron).get(g.current_user.id)
+    checkout = patron.checkouts[0]
+    assert checkout.due_on == date.today() + timedelta(
+        days=current_domain.config["custom"][validity_days_config]
+    )
+
+
+@then("the hold is marked as checked out")
+def hold_marked_checked_out():
+    patron = current_domain.repository_for(Patron).get(g.current_user.id)
+    hold = patron.holds[0]
+    assert hold.status == HoldStatus.CHECKED_OUT.value

tests/lending/app/bdd/checkout_handlers/test_checkouts.py

@@ -0,0 +1,5 @@
+from pytest_bdd import scenarios
+
+from .step_defs.checkout_steps import *  # noqa: F403
+
+scenarios("./features")